%0 Journal Article
%T 油罐车火灾下考虑混凝土高温爆裂的PC箱梁承载能力<br>Bearing capacity of PC box girder based on concrete spalling？？under fuel tanker fire exposure
%A 张岗
%A 侯章伟
%A 宋超杰
%A 贺拴海
%A 李源
%J 长安大学学报(自然科学版)
%D 2018
%X 针对油罐车火灾对预应力混凝土桥梁的破坏过程，选取桥梁工程建设中应用较为广泛的预应力混凝土(PC)箱梁为研究对象，建立油罐车火灾下预应力混凝土箱梁桥混凝土高温爆裂的“三级指标”，并设定了相应油罐车火灾下混凝土的爆裂场景，采用单元生死技术模拟混凝土高温爆裂特征，分析考虑混凝土高温爆裂的预应力混凝土箱梁截面温度场的完整分布形态，计算混凝土不同高温爆裂指标下的预应力混凝土箱梁极限承载能力，拟合并建立计算公式。研究结果表明：截面关键点的温度曲线呈三阶段上升趋势；爆裂导致混凝土截面的温度在传导过程中产生突变，温度分布以爆裂后截面形态分层递进；混凝土的高温爆裂使钢束、钢筋的强度显著下降；混凝土的爆裂深度越大，正截面抗弯承载能力下降越快；混凝土发生重度爆裂，延火时间180 min时，箱梁跨中截面的抗弯承载能力从未爆裂时的60.73%降至14.87%，箱梁？？L？？/4截面（？？L？？为跨径）的抗弯承载能力从未爆裂时的64.37%降至19.37%；混凝土高温爆裂不同深度下预应力混凝土箱梁桥抗弯承载能力衰变呈现多阶段特征。混凝土爆裂对预应力混凝土箱梁的截面温度分布和抗弯承载能力影响显著，提出的考虑爆裂的承载能力计算公式简单实用。<br>Aiming at the damage characteristics of prestressed concrete bridge caused by oil tanker fire， a prestressed concrete (PC) box girder, which is widely applied in bridge construction, was selected as the research object, and a three？？grade index of concrete spalling at elevated temperature was proposed. The concrete spalling conditions under hydrocarbon fire scenarios were defined, and the birth？？death element technique was applied to simulate the concrete spalling. The complete distribution profile of the cross？？sectional temperature within the PC box girder considering concrete spalling was analyzed. The ultimate flexural capacity of the PC box girder under different spalling indices was calculated, and the calculation formula was proposed. The results show that the temperature curve of key points in the cross section has a three？？stage rise. The concrete spalling can lead to a sudden change of cross？？sectional temperature, and the temperature shows a layer distribution toward the inside of the cross section after concrete spalling. The strength of the prestressed strand and reinforcement decreased significantly as a result of concrete spalling. With a larger depth of concrete spalling, the flexural capacity decreased with a faster step. When severe spalling of concrete occurred at 180 min, the flexural capacity of a PC box girder at midspan decreased from 60.73% to 14.87%, and the flexural capacity of the PC box girder at ？？L？？/4 section (？？L？？ is the span) decreased from 64.37% to 19.37%. Flexural capacity demonstrated a multistage descent at different depths of concrete spalling. Concrete spalling has a significant effect on the flexural capacity and temperature distribution of PC box girders. The proposed formula considering concrete spalling is simple and practical, and it can be used to evaluate the fire resistance of the PC box girder. 4 tabs, 10 figs, 26 refs.？
%K 桥梁工程
%K 预应力混凝土箱梁
%K 有限元
%K 火灾
%K 爆裂
%K 温度场
%K 承载能力&lt
%K br&gt
%K bridge engineering
%K PC
%K FEM
%K fire
%K spalling
%K temperature
%K flexural capacity
%U http://zzszrb.chd.edu.cn/oa/DArticle.aspx?type=view&id=1806011